CVE-2026-23191

In the Linux kernel, the following vulnerability has been resolved:

ALSA: aloop: Fix racy access at PCM trigger

The PCM trigger callback of aloop driver tries to check the PCM state and stop the stream of the tied substream in the corresponding cable. Since both check and stop operations are performed outside the cable lock, this may result in UAF when a program attempts to trigger frequently while opening/closing the tied stream, as spotted by fuzzers.

For addressing the UAF, this patch changes two things:

• It covers the most of code in loopback_check_format() with cable->lock spinlock, and add the proper NULL checks. This avoids already some racy accesses.
• In addition, now we try to check the state of the capture PCM stream that may be stopped in this function, which was the major pain point leading to UAF.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/5727ccf9d19ca414cb76d9b647883822e2789c2e
• https://git.kernel.org/stable/c/826af7fa62e347464b1b4e0ba2fe19a92438084f
• https://git.kernel.org/stable/c/bad15420050db1803767e58756114800cce91ea4